The Doctor’s sonic screwdriver has become steadily more iconic as the years progressed. Despite disappearing in the middle of the Time Lord’s career, it’s now firmly – not to say commercially – integrated into the Doctor Who canon. So there’s no more to say on the subject, right?
Wrong.
Earlier this year, the Sonic Screwdriver …

COMMENTS

hurrah!

The Sonic Screwdriver X-Prize?

Given that Qualcomm has persuaded the X-Prize foundation to run a $10 million prize competition for someone coming up with a healthcare device similar to the Tricorder, how about lobbying someone like ARM to fund the equivalent Sonic Screwdriver prize?

Re: But, but, but

Batteries.

If you want more space for the electronic gubbins, and less for the batteries, CR2s (3V lithium - 27mm x 15.6mm diameter) and CR123As (3V lithium - 34.5mm x 17mm diameter), as used to be used in many a film camera, can come in handy.

Back in the day

The reason why this works for both 9 and 3 volts...

(This is heavily simplified as most people here probably won't understand the details)

This detector is built with a field effect transistor. It's a kind of electronically activated switch. Normally it switches based on the voltage at it's "Gate" connector (the one going to the antenna). It switches between the source and drain connectors so current can flow and the LED can light up.

Now one thing that's important with LEDs is that the amount of current going through it is not to high. Usually this is done with a resistor. However the current a resistor lets through is proportional to the voltage you apply to it. That's why you need larger resistors for higher voltages...

However field effect transistors have a secondary effect. If you pass to much current through them while "switched on", they will gradually "switch off" so less current goes through it. This kinda causes an equilibrium where the current is limited at a certain value. Apparently with this transistor it happens just in the range that's acceptable with LEDs.

Re: The reason why this works for both 9 and 3 volts...

Well... I've googled and googled and I just can't for the life of me figure out......

"Somewhat to the surprise of everyone I showed it too, the constructed Sonic Screwdriver works as advertised, the body lights up red when the upper band is touched, and the greed LED can indeed detect the unseen forces of static electricity."

Greed LED

GREED LED

Avarice-emitting diode?

___

Also: closely examine the tricks listed on RSCD Ridiculously Sensitive Charge Detector site. During humid conditions one can turn the LED on and off by scuffing a shoe on carpet ...but on a low-humidity day one can turn the LED on and off by slightly moving just one single toe.

http://www.amasci.com/emotor/chargdet.html#5

Prepare to wiggle your toe, then proceed to ask yes/no questions of your activated S.S. (Capt Pike blinks twice for "No.") Show your audience that it lights up when you smirk at it, but refuses to light up no matter how intense others' gurning. Or, detect either high blood-alcohol levels or disguised aliens (where the light turns on as you wave it under certain noses but not others'.) All this under low humidity conditions, because if otherwise, your audience may notice your larger foot-movements against the carpet.

"Somewhat to the surprise of everyone I showed it too, the constructed Sonic Screwdriver works as advertised, the body lights up red when the upper band is touched, and the greed LED can indeed detect the unseen forces of static electricity."

Nice

I am working on a neutrino detector for it but the tricky part is making the K40, please can someone help with this? Growing a pure crystal by differential crystallisation using the slighly different melting points of K39 and K40 is going to take aaaaaaages.

Takes me back awhile....

When I worked for BT (Post Office then), we got some of those new-fangled FET things. 2N3819. Bloody expensive then - at least a quid, which in the 1970's would have bought a couple of bevvies.

My boss used to get a fit of the vapours when I'd test 'em by sticking an AVO-8 between source and drain, then comb my hair to watch the needle thrash about. They were J-FET's - no real harm if I was careful

(Didn't dare try with the much more expensive and fragile 40673 dual-gate IGFET's. Man, you had to be careful not to remove/dislodge the shorting ring 'til they were soldered in place!).

As to the writer's cct, adding a UJT, a cap., resistor and a piezo loudspeaker - THEREMIN!!

Sonic Screwdriver? Who uses those any more?

One of the last doctor's is now advertising stuff for Virgin and I bet if he used his sonic screwdriver or its series X derivative in the ads the BBC would probably sue for some contractual breach or infringement of the commercial (cashcow?) entity that is/was/never will be Doctor Who?

Heh

I might accept that challenge.

Making a Tesla Coil screwdriver would be possible, came up with a design based on a magnifier setup using piezoelectric transformers harvested from dead flat panels and a custom wound double resonant secondary with a pair of antiparallel windings.

Also you can now get <300nm burner diodes which will allow air ionisation so the spark follows a well defined line from the device.

Deus IN machina! Deus IN machina!

The sonic screwdriver is not deus ex machina at all, it is deus in machina. Deus ex machina requires a previously unmentioned outside force to affect the course of events, but the sonic screwdriver is an established element of the Doctor Who story universe, therefore it is not an outside force by any stretch of the imagination.